The invention relates to a safety stirrup with a web plate and with a U-shaped upper part which has two lateral legs and an upper base region, the two lateral legs being each provided with an articulated area having swivel axles running across the plane defined by the upper part and two connecting areas being each provided with a bore for a swivel axle.
This safety stirrup, which is being offered for sale, is standing the test very well. The articulated areas are provided in the lower part of the two lateral legs, which is adjacent to the web plate. They allow the web plate to swing relative to the upper base region and to the adjacent part of the lateral legs which is rigidly mounted to the upper base region above the articulated areas.
In the safety stirrup of the art, two swivel axles are provided in either articulated area. For the formation of the articulated area, an incision running parallel to the mentioned plane and receiving a connecting part is provided in either of the two associated connecting areas. The associated swivel axles are inserted in a bore provided across the mentioned plane in either connecting area.
Due to the fact that the two connecting areas of either articulated area are connected by only one connecting part, the safety stirrup of the art is mechanically weak when loaded across the plane of the plate-shaped connecting parts, that is across the mentioned plane. The construction of the articulated areas is not satisfactory either. It happens over and over again that the protecting hose sheathing each articulated area wears through. Additionally, the articulated areas are often quite sluggish.
That is where the invention comes to bear. Its object is to develop the safety stirrup of the type mentioned above in such a way that it becomes safer, better suited to the needs of a user and easy-running in the articulated areas.
Footing on the safety stirrup of the type mentioned above, the solution of this object is to provide each articulated area with at least three swivel axles, each connecting area with a semicircular part limited by two flattened areas running parallel to the mentioned plane and to connect together two adjacent hinge pins by means of two connecting parts each.
This safety stirrup has at least one more swivel axle, called in the following free swivel axle, which is located between the two swivel axles provided in either of the two opposite connecting areas of an articulated area. Preferably, two free swivel axles are provided between the swivel axles of the connecting areas so that the safety stirrup has four joints in each articulated area. Due to the number of at least three swivel axles or hinge pins for each articulated area, each articulated area is much more flexible and easy-running than the articulated area in the safety stirrup of the art. The protection hose requires therefor less solidity or rigidity, as it may be measured in Shore hardness for example. Thus, each articulated area is constructed at lower cost.
It is particularly advantageous that at least one free swivel axle is provided for each articulated area, since this ensures the adaptability of a safety stirrup constructed according to this feature. Indeed, according to the wishes of a user, the leg can be lengthened by inserting additional swivel axles. Safety stirrups may thus better adjust to the wishes of the user. It is even possible to have one of the legs constructed with more or less swivel axles than the other leg.
A particular advantage of the invention is that two adjacent swivel axles are connected together by two connecting parts arranged parallel to one another. Thus, buckling movements across the swivel axles and across the planes of the connecting parts are nearly impossible. The connecting parts are forming couples whereas the two connecting parts of either couple are arranged at the biggest possible distance from each other. This spacing should amount to at least 2, preferably at least 4 mm. The invention takes advantage of an idea used also for the chains of bicycles, motorbikes and the like. The invention preferably uses connecting parts having essentially the shape of an 8, as they are also used in such chains. The invention uses thus for the construction of the articulated areas component parts as they are known from the above-mentioned chains. Since such chains are extremely strong and articulated and since they stood the test in practical operation, their qualities have also been adopted for the safety stirrups.
In either of the free swivel axles, spacer blocks are also used to the same effect. The spacer blocks used therefor are the same as those used for bicycle chains or the like.
As opposed to the state of the art, the design of the connecting areas is completely different. They are no longer provided with an incision, but are limited by two parallel flattened areas showing outwards away from each other and extending parallel to the mentioned plane and by an arched area arranged crosswise. This arched area is preferably an arc of a circle. The bore for the swivel axle is located in its center.
Two connecting areas constructed according to this teaching as they are provided for either articulated area are linked together by piece parts of a chain of the type mentioned above. A piece of an already assembled chain may be used. In this case, the free swivel axles do not require any particular phase of operation since the free swivel axles are already there. The distance between the two flattened areas is then adapted to the clearance between two connecting parts of a commercial chain. Hinge pins as they are used in chains are also used to establish the swivelling connection in the area of the hinge pins of the connecting areas.
By using pieces of chains to construct the articulated areas, the inner casing of a sheathing hose is spared and incisions and so on as they were to be found in the safety stirrup mentioned at the beginning, are avoided. The thickness and depth of the pieces of chain inserted square with the corresponding dimensions of the adjacent areas of the legs. Thus, the pieces of chain do not protrude.